PFAS Accountability Act of 2021 This bill provides a cause of action under the Toxic Substances Control Act for individuals or classes of individuals who were significantly exposed to perfluoroalkyl or polyfluoroalkyl substances, commonly referred to as PFAS. These substances are man-made and may have adverse human health effects. A variety of products contain the compounds, such as nonstick cookware or weatherproof clothing. Specifically, the bill provides a cause of action those who were significantly exposed to PFAS (or have reasonable grounds to believe they were exposed) against persons who engaged in any portion of a manufacturing process that created the PFAS and foresaw (or reasonably should have foreseen) the creation or use of PFAS would result in human exposure. The bill authorizes a court to award medical monitoring to claimants if (1) they have been significantly exposed to PFAS, (2) they have an increased risk of developing a disease associated with such exposure, (3) the increased risk provides a reasonable basis to conclude that periodic diagnostic medical examinations is necessary, and (4) the medical examinations are effective in detecting a disease associated with PFAS exposure. The bill establishes a presumption of significant exposure to PFAS if the claimant (1) provides medical results proving the presence of PFAS in the body, or (2) demonstrates the defendant's manufacturing process created the PFAS to which the claimant was exposed and the PFAS were released into one or more areas where the claimant would have been exposed for at least one year.